docs: add doc strings for ContentHandler classes

Author: jaredhendrickson13

pfSense-pkg-RESTAPI/files/usr/local/pkg/RESTAPI/ContentHandlers/JSONContentHandler.inc

@@ -13,14 +13,30 @@ use RESTAPI\Responses\ValidationError;
 class JSONContentHandler extends ContentHandler {
     public string $mime_type = 'application/json';
 
+    /**
+     * Obtains the client's raw request body content.
+     *
+     * @return string The raw content from the request body.
+     */
     public function get_content(): string {
         return file_get_contents('php://input') ?: '';
     }
 
+    /**
+     * Encodes the given content as JSON.
+     * @param mixed|null $content The content to encode.
+     * @return mixed The encoded content.
+     */
     protected function _encode(mixed $content = null): mixed {
         return $content ? json_encode($content) : [];
     }
 
+    /**
+     * Decodes the given content from JSON.
+     * @param mixed|null $content The content to decode.
+     * @return mixed The decoded content.
+     * @throws ValidationError If the content could not be decoded.
+     */
     protected function _decode(mixed $content = null): mixed {
         # Allow empty strings, but convert it to an empty array.
         if (empty($content)) {

pfSense-pkg-RESTAPI/files/usr/local/pkg/RESTAPI/ContentHandlers/URLContentHandler.inc

@@ -11,10 +11,20 @@ use RESTAPI\Core\ContentHandler;
 class URLContentHandler extends ContentHandler {
     public string $mime_type = 'application/x-www-form-urlencoded';
 
+    /**
+     * Obtains the client's request data from PHP's $_GET superglobal.
+     *
+     * @return array The request data parsed from the query string.
+     */
     public function get_content(): array {
         return $_GET;
     }
 
+    /**
+     * Decodes the given content from URL encoded data and makes basic type interference.
+     * @param mixed|null $content The content to decode.
+     * @return mixed The decode content.
+     */
     protected function _decode(mixed $content = null): mixed {
         # Loop through each query string item and check for expected data types
         foreach ($content as $key => $value) {